1. Technical Field
The present invention relates to an optical printed circuit board which can transfer optical signal and electric signals simultaneously, and a method of fabricating the optical printed circuit board.
2. Description of the Related Art
Optical connection technology is widely used in data transmission between systems separated several to several hundreds of meters, data bus transmission between back planes in systems separated several tens of centimeters to several meters, connection between boards separated several tens of centimeters, and data links between chips separated several to several tens of centimeters, etc.
Various connecting methods are used, such as using free space connection, optical fiber ribbons, and polymer optical waveguides, etc. In order to apply optical connection to boards having a relatively short transmission distance, the connecting method should be improved to be applicable to present printed circuit board technology.
An optical printed circuit board according to prior art is disclosed in Korean patent publication No. 10-2005-0072736. The optical printed circuit board has dielectric layers formed on both sides of the optical waveguide respectively and a reflecting surface that refracts the incident light vertically. Also, transmission chips and receipt chips are mounted at the circuit pattern formed in the printed circuit board. On the chips, VCSEL's (Vertical-Cavity Surface-Emitting Lasers) or photodiodes are protruded downward, so that light is irradiated or received in the reflecting surface. The irradiated light is refracted at the reflecting surface to be transmitted through the optical waveguide.
The optical waveguide according to the prior art has a gap between the photodiode or VCSEL and dielectric layer, so that optical connection efficiency is decreased due to the diffusing property of light irradiated or refracted on the VCSEL or the photodiode. Also, the surface of the dielectric layer is given roughness in order to form a metal layer easily, but such a roughened surface leads to light loss.